When to update?

With no special requirements, should I wait for Canonical to prompt an update to 6.3 on my Ubuntu 18.04 LTS?

With no special requirements (= no problems with current state), why would you want an upgrade at all?

On Linux, the best answer to “when to update” is always “whenever the update applet says so.” Unless you enjoy tinkering with your system, always use official repositories!

The release report made it look attractive, but since I am not a tinkerer I will leave well enough alone. Thank you.

Quoting @frankp: “The release report {notes?} made it look attractive, …”
If you want to see new features working to be able to estimate their value, you need the new version running, of course, best in a “testing mode”. In this case you should install the new version -or a dev version of the release to come- in parallel to your current “production” version.
See Development versions | LibreOffice - Free Office Suite - Based on OpenOffice - Compatible with Microsoft (Don’t mind the flaw in the text.) and
Installing several versions of LibreOffice in parallel - The Document Foundation Wiki
Be careful!

Hi

Another point to think about: new versions not only bring new features or bug fixes, they also fix security vulnerabilities.

Regards